Rewinding machine to rewind web material on a core for rolls and corresponding method of winding

ABSTRACT

In a rewinding machine for winding web material onto a core to form rolls which has an unusual capability for accurate regulation of the winding, the web material is supplied to a winding drum and is transferred to the core to form the roll. The core is supported, rotated in controlled manner, and transported along a path in which the roll of web material wound on the core is enlarged whilst bearing continuously on the winding drum.

BACKGROUND OF THE INVENTION

[0001] The subject of the present invention is a rewinding machine forwinding material in web form onto a core to form rolls, as well as acorresponding winding method.

[0002] It is known that the winding of rolls of web material onto coressuch as, for example, the winding of paper tissue onto cardboard cores,is performed by means of plant comprising apparatus for continuouslyunwinding paper from a reel. Downstream of this apparatus there is awinder or rewinding machine which winds the paper onto a plurality ofcores to form the rolls. Downstream of the rewinding machine in turnthere is apparatus for cutting the finished roll into a plurality ofsmall rolls.

[0003] In particular, two methods are known for winding the web materialonto the core.

[0004] In a first method, known as central winding, the core is fittedon a motor-driven spindle of the same length as the core, for rotatingthe core about its axis. When an edge of the web material has been stuckto the core, the desired quantity of web material is wound onto the coreby rotation of the spindle, to form the roll. Upon completion of thewinding, the roll is removed from the working area and the spindle istaken out of the core and returned to the working area by arecirculating device.

[0005] A machine of the type described above is known from U.S. Pat. No.5,660,350.

[0006] Although these machines have considerable advantages, they havethe disadvantage that it is necessary to use spindles and cores oflimited axial length. In fact, during the roll-forming step, long coresfitted on long spindles would clearly be subject to bending forces whichwould set up vibrations such that accurate and even winding with uniformcompactness throughout the winding operation would be impossible,resulting in an irreparable deterioration in the quality of the product.

[0007] A second method also used for winding web material onto cores isknown as peripheral winding. According to this method, after the corehas been brought up to winding drums so as to cause the web material toadhere to the core, the core is driven by the drums in a winding area inwhich the roll being formed is acted on peripherally by three drums,leaving the core free to float in the web material which is being woundthereon.

[0008] A machine of the type described above is known from WO 99/42393in which, upon completion of the winding, the core is removed from thewound roll, to form rolls without support cores.

[0009] However, it is clear that, although this latter solution issimpler in operation, it has many disadvantages.

[0010] First of all, peripheral winding, by its nature, does not allowthe rate of rotation of the core to be controlled directly since thecore is floating in the winding area between the three winding drums.With these known rewinding machines, it is therefore impossible tocontrol the tension of the web material directly during its windingaround the core, making it particularly difficult to produce rolls whichhave a uniform consistency throughout their thickness. This disadvantageis particularly important above all when a particularly soft roll is tobe produced, as is required by some markets such as, for example, theUnited States market. In particular, if the web material is suppliedwithout considerable pretensioning, it is almost impossible to ensurethe same compactness of the roll both in the initial stages of thewinding and in the final stages of the winding and, in the case ofparticularly soft rolls, the core may even be eccentric relative to theaxis of the roll upon completion of the winding.

SUMMARY OF THE INVENTION

[0011] The problem upon which the present invention is based is that ofproposing a rewinding machine for winding web material onto a core toform rolls which has structural and functional characteristics such asto overcome the disadvantages mentioned above with reference to theprior art cited.

[0012] This problem is solved by a rewinding machine for winding webmaterial onto a core to form rolls according to claim 1.

[0013] In the rewinding machine proposed, the web material is suppliedto a winding drum and the web material is transferred to the core toform the roll.

[0014] The core is advantageously supported, rotated in controlledmanner, and transported along a path in which the roll of web materialwound on the core grows larger whilst continuously bearing on thewinding drum.

[0015] The problem is also solved by a method of winding web materialonto a core to form rolls according to claim 50.

[0016] Advantageously, in the proposed method, the web material issupplied at a predefined supply speed, the web material is guided, in awinding region, at a speed substantially corresponding to the supplyspeed, and the core is supported and is rotated in a manner such as tohave a predefined peripheral velocity. The core is moved along a workingpath formed between a pick-up position and a release position, passingfrom a position of initial contact of the core with the web material, inorder to pick up the web material, and continuing towards a finalwinding position, through a size-enlargement or increasing portion inwhich the material is wound on the core to form the roll. The core isthus influenced in a manner such that the material is wound onto thecore whilst the roll being formed is kept bearing against the windingdrum throughout the increasing portion of the working path.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further characteristics and the advantages of the rewindingmachine according to the invention will become clear from the followingdescription of a preferred embodiment thereof, given by way ofnon-limiting example with reference to the appended drawings, in which:

[0018]FIG. 1 is a partially-sectioned axonometric view of a rewindingmachine,

[0019]FIG. 2 is a partially-sectioned view of the rewinding machine,taken on the arrow II of FIG. 1,

[0020]FIG. 3a is an axonometric view of a detail of the machine of FIG.1,

[0021]FIG. 3b is a partially-sectioned side view of a further detail ofthe detail of FIG. 3a,

[0022]FIG. 4 is a partially-sectioned view, taken on the arrow IV ofFIG. 1, of another detail of the rewinding machine,

[0023]FIG. 5 shows the detail of FIG. 4, from above, in a firstoperating stage,

[0024]FIG. 6 shows the detail of FIG. 4, from above, in a secondoperating stage,

[0025]FIG. 7 is a partially-sectioned axonometric view of yet anotherdetail of the rewinding machine of FIG. 1,

[0026]FIG. 8 is a schematic perspective view of the operating andcontrol system of the rewinding machine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] With reference to the drawings., a rewinding machine, generallyindicated 1, comprises a support frame 2, a supply device 3 forsupplying cores 5 to a winding assembly 4, as well as means 6 forsupplying web material 7 to be wound onto the cores to form rolls 8(FIG. 2).

[0028] The support frame 2 comprises opposed shoulders 9 connected byself-levelling bolts 10 to support plates 11 fixed to a base 12. Theshoulders 9 are connected to one another by a plurality of cross-members13 constituting support elements for further components of the machine.According to one embodiment, the cross-members 13 are tubular profiledsections, for example, having square cross-sections to provide securesupport surfaces for the further components of the machine. The supportframe 2 defines a machine space which is open on three of its sides forthe operative connection of the machine to a web-material plant (FIGS. 1and 2).

[0029] The web material 7 coming from apparatus for unwinding itcontinuously from at least one reel or “mother reel” (not shown) issupplied to the machine 1. For example, the web material 7 comprises oneor a plurality of webs of paper, particularly tissue, which, onceunwound from one or more reels, may undergo known intermediate printingand/or embossing treatments before being supplied to the rewindingmachine 1. According to one embodiment, the web material follows asupply path 14 defined by a plurality of drums arranged parallel to oneanother and supported rotatably on the shoulders 9 of the support frame2. The supply means 6 move the web material 7 along the supply path 14at a predefined supply speed. The supply means 6 comprise at least onepulling drum 15 which transmits the movement to the web material whichextends partially around it. The pulling drum is operatively connectedto an electric motor 16, for example, a “brushless” motor supported on ashoulder 9 and connected by a belt, preferably a toothed belt, to apulley fitted on one end of the pulling drum 15. Upstream of the pullingdrum 15 there is a roller 17 which, as well as obliging the web materialto follow a tortuous path to force it to extend around an upper portionof the surface of the pulling drum 15, has a transducer, for example, aload cell, operatively connected to the roller 17, for detecting thetension imposed on the web material by the pulling drum. The motor ofthe pulling drum is operated and controlled in the manner which will bedescribed in detail below.

[0030] Parallel to the pulling drum is a unit 18 for pre-cutting the webmaterial 7.

[0031] The web material 7, pulled by the supply means 6, is supplied tothe winding assembly 4. This comprises a winding drum 23 which guidesthe material 7 in a winding region 24, defining a first side thereof.The winding drum is supported so as to be freely rotatable on theshoulders 9 of the frame 2 in order to be driven by means of anoperative connection to an electric motor 25, so as to have a peripheralvelocity substantially corresponding to the speed of supply (v) of theweb material 7. For example, a brushless motor supported on one of theshoulders 9 of the support frame 2 is connected by a belt, preferably atoothed belt, to a pulley keyed to one end of the winding drum 23.According to a further embodiment, a second winding drum 26 is provided,opposite the first winding drum 23 and arranged so as to define theregion 24 for the winding of the web material on the opposite side tothe first winding drum. According to yet another embodiment, the firstand second winding drums 23 and 26 are arranged in a manner such that adistance or space of dimensions substantially equal to the transversedimensions of a core 5 is left between their cylindrical surfaces. Thesecond winding drum 26 is also preferably supported so as to be freelyrotatable on the shoulders 9 of the support frame 2 and is operativelyconnected to an electric motor 27 for rotating it at a speedsubstantially corresponding to the speed of supply (v) of the webmaterial 7. As for the first drum, the motor of the second drum is, forexample, a brushless motor supported on one of the shoulders 9 of thesupport frame 2 so as to be connected by means of a belt, preferably atoothed belt, to a pulley keyed to an end of the second winding drum 26.The motors of the winding drums are also operated and controlled in themanner which will be described in detail below.

[0032] Beside the first and second winding drums 23, 26 and on the sidefrom which the web material 7 is supplied, is the device 3 for supplyingcores, for example, tubular cardboard cores 5. This device comprises apair of conveyor belts 28 each provided with a plurality of supportscoops 29 for housing and firmly supporting respective ends of cores 5.The conveyor belts 28 are arranged parallel to one another and in amanner such as to pick up cores 5 from a store 30 in order to lift themand to discharge them into a core-supply chute 31. For its movement, thecore-supply device 3 comprises a geared motor unit 32 keyed to a shaftprovided with pulleys for housing the conveyor belts in order to movethem synchronously. According to one embodiment, the geared motor unit32 is operatively connected to an actuator activated by a transducer fordetecting a lack of cores 5 in the supply chute 31, such as, forexample, a photocell which is disposed at a predetermined height on thechute and can detect the presence of the desired number of cores 5 onthe chute 31. In particular, the chute comprises plates 33 provided withsurfaces for the sliding of the cores, these surfaces extending to thevicinity of the space provided between the two winding drums 23, 26. Acage 34 is associated with the chute plates 33 for preventingsuperposition of the cores which are urged towards the end close to thedrums by gravity. Flat springs 35 projecting from the chute plates 33 atthe bottom and from the cage 34 at the top can restrain a core 5 in apick-up position “L” in the vicinity of the winding region 24.

[0033] A working path “P” for the core is formed, starting from thepick-up position and extending between the two winding drums. In theembodiment shown in FIG. 2, the working path “P” is straight. However,the path may adopt different shapes provided that, starting from thepick-up position “L”, it extends from a position of initial contact ofthe core with the web material, indicated “F” in FIG. 2, through a finalwinding position “E”, terminating in a release position “U”. Forconvenience of description, the working path “P” is divided into anapproach portion disposed between the pick-up position “L” and theinitial contact position “F”, a size-enlargement or increasing portiondisposed between the initial contact position “F” and the final windingposition “E”, and an expulsion portion disposed between the finalwinding position “E” and the release position “U”.

[0034] The core 5 is advantageously moved along the working path byvirtue of the provision of gripping means for supporting it, means formoving it along the working path, means for its controlled rotation soas to wind the web material onto the core to form the roll, as well asmeans for influencing the roll as it bears continuously on at least oneof the winding drums in the increasing portion of the working path inwhich the web material is wound onto the core. These latter meanspreferably influence the roll being formed as it bears continuously onthe two winding drums which define the winding region on two sides. Thecore is then brought to the release position “U” where release meansallow the roll 8 to fall onto a discharge chute 36 so as to be conveyedto subsequent known stations for gluing, cutting into small rolls andpackaging.

[0035] According to one embodiment, at least one pair of opposed pins37, which can be operatively associated with the insides of the ends ofthe tubular core 5, is associated with each side of the set of windingdrums 23, 26 or, in other words, is associated with the ends of the core5 in any position thereof on the working path “P”. Each pin 37 has acylindrical body on which the end of a core 5 can be fitted withinterference. The body of the pin 37 has a frustoconical free end 38 forfacilitating the insertion of the pin 37 in the end of the core 5 and anannular projection 39 for the abutment of the edge 40 of the core 5. Atleast one longitudinal channel 41 and preferably two opposed channels orseveral uniformly spaced channels, are formed in the cylindrical bodyand house retaining means for engaging the inner surface of the wall ofthe tubular core to ensure a firm grip of the pin even during itsmovement. According to one embodiment, the retaining means comprise atleast one resilient expansion device 42 for gripping the inner surfaceof the tubular core radially with pressure. According to a furtherembodiment, the device has at least one blade-like element 43 acting tooppose slipping of the pin out of the tubular body of the core. Forexample, the device is a spring 42, the body of which is wrapped arounda support pin fixed to the wall of the channel 41 so as to allow a firstend arm 44 of the spring, provided with a bearing portion, to abut thebase of the channel 41, leaving a second arm 43, provided with ablade-shaped end, projecting partially resiliently outwardly relative tothe pin and facing towards the annular projection 39 thereof. The pin 37is arranged on the free end of a shaft 45 housed so as to be freelyrotatable in a support 46. Transducers are advantageously operativelyassociated with the shaft 45 for detecting the forces transmitted by thepin 37 to the core 5 and, in particular, the axial pulling force on thecore 5 and the effect of the transmission torque, for example, bydetecting the rate of rotation imposed on the core by the pin. A pulleyis keyed to the shaft 45 of each pin for operative connection to anelectric motor 47 operated and controlled in the manner which will bedescribed in detail below, so as to rotate the core at a predefinedspeed (FIGS. 3a and 3 b).

[0036] According to one embodiment, independent means are provided forthe controlled rotation of each end of the core 5.

[0037] The at least one pair of opposed pins 37 is moved towards andaway from the opposite ends of the core as well as along the workingpath “P”. Preferably, an operative connection is provided between themeans for gripping the core 5 and the means for moving the core 5.

[0038] According to one embodiment, each of the gripping means isoperatively connected to a table with crossed guides (for example acompound table), generally indicated 48 in the drawings. In particular,the means for moving the core comprise opposed carriages 49 provided onboth sides of the machine 1 for supporting the gripping means comprisingthe pin 37 and the respective motor 47 for rotating the pin. Thecarriages 49 are movable in controlled manner along movement axesarranged, for example, parallel and perpendicular to the working path“P”. According to one embodiment, the movement axes comprise, for eachside of the rewinding machine 1, a pair of brackets 50 which arecantilevered on the shoulders 9 of the support frame and on which guides51 are arranged parallel to one another and perpendicular to the workingpath “P”. The transverse guides 51 are spaced apart so that the entireworking path “P” is included between them, in the manner which will beexplained further below. The transverse guides 51 support, in a freelyslidable manner, sliding blocks 52 fixed to a single cross-member 53 onwhich a guide 54 parallel to the working path “P” is provided. Thecross-member 53 is operatively connected to an actuating device forcausing it to slide on the transverse guides 51 by means of the slidingblocks 52. According to one embodiment, a rod 55 of a cylinder andpiston unit 56 supported firmly on the shoulders 9 of the support frame2 is connected to the cross-member. For example, the cylinder and pistonunit is of the pneumatic or hydraulic type and is operated in controlledmanner, in the way which will be described in detail below. The parallelguide 54 supports, in a freely slidable manner, the carriage 49 carryingthe pin 37. The carriage 49 is operatively connected to a device for itscontrolled movement along the guide 54 parallel to the working path “P”.According to one embodiment, a rack 57 fixed firmly to the carriage 49is meshed with a pinion of a geared motor unit 58 supported firmly onone of the sliding blocks 52. The geared motor unit 58 is operativelyconnected to a operating and control device in the manner which will bedescribed in greater detail below (FIGS. 2 and 3a).

[0039] The guides 51 arranged transverse the path “P” and the guides 54which are parallel thereto are preferably straight and enable thegripping means to be moved in a working plane “W” (FIG. 3a).

[0040] Advantageously, in addition to the provision of independent meansfor moving each end of the core, twin independent movement means areprovided for each side of the rewinding machine 1 and can be associatedwith ends of cores for multiple movements thereof in the same workingarea, for example, in the working plane “W”, in the manner which will bedescribed in detail below. For example, identical movement means areprovided for each side of the rewinding machine and are arrangedreflectively symmetrically with respect to the working plane “W” ofmovement of the gripping means. These reflectively symmetrical movementmeans have corresponding elements which are indicated in the drawings bythe same reference numerals provided with apostrophes “ ”. Twinindependent gripping means, controlled rotation means, movement means,and means for influencing the core 5 bearing on the winding drum 23 willthus be provided for each side or side wall of the rewinding machine.

[0041] With regard to the movement of the pair of opposed pins 37, 37′towards and away from the core 5, the means for the movement of the corecomprise further means for pulling the core 5 axially during the windingof the web material. According to one embodiment, this function isperformed by the cross-member 53, 53′ slidable on the transverse guides51, 51′, and moved by the cylinder and piston unit 56, 56′.

[0042] Each of the above-mentioned devices for moving the drums and thecores is operatively connected to a corresponding operating devicewhich, for convenience of illustration has been indicated by a singlereference element, indicated 59 in FIG. 8. These operating devices 59are controlled by one or more control devices 60, preferably withfeedback (FIG. 8). In particular, the motor 16 for rotating the pullingdrum 15 is operated in controlled manner, for example, by a signalproportional to the tension exerted on the web material 7, detected bythe load cell provided in the roller 17 and fed back to the controldevice 60. According to one embodiment, the control imposed on theoperation of the pulling drum 15 constitutes a reference for theoperation, in synchronism or out of phase therewith, of the windingassembly 4 and of the core-supply device 3, as well as of the means forgripping, rotating and moving the core. In particular, the winding drum23 is operated in controlled manner, advantageously with feedback of itsrate of rotation, so as to achieve a peripheral velocity thereof, thatis, a speed of its curved surface in contact with the web material,substantially corresponding to, greater than, or less than the speedimposed on the web material 7 by the pulling drum 15 (the supply speed“v”). The second winding drum 26 is also driven in controlled mannerwith feedback of its rate of rotation so as to achieve a peripheralvelocity thereof substantially corresponding to, greater than, or lessthan the supply speed of the web material 7. By controlled regulation ofthe relative speeds of the two winding drums 23 and 26, it is possibleto regulate the winding of the web material onto the core andconsequently the consistency of the roll. With regard to the means forrotating the core 5, there is provision for their controlled operationwith speed feedback which, with a knowledge of the thickness of the webmaterial, for example, because it is predefined or is detected bysuitable transducers, can achieve a peripheral velocity of the roller 8being wound substantially corresponding to, greater than or less thanthe supply speed of the web material 7. A controlled enlargement orincrease of the roll of web material is thus achieved. With a speedsubstantially corresponding to the supply speed, a roll with uniformcompactness is obtained, with a speed greater than the supply speed, asmall, tight and compact roll is obtained, and with a slower speed, asoft and voluminous roll is obtained, respectively. According to oneembodiment, a device is interposed between the gripping means and themeans for the controlled rotation of the core for detecting the forcetransmitted to the core. This device for detecting forces transmitted tothe core is preferably operatively connected to the device for bringingabout and controlling the rotation of the core and the axial pulling ofthe core. In particular, by virtue of the device which detects theforces transmitted to the core by the means for its rotation, it ispossible to detect the occurrence of torsional, and principallyflexural, vibrations, during the winding of the web material thereon.The provision of independent means for the controlled rotation of eachend of the core advantageously permits a synchronized or out-of-phasemovement of the two ends of the core in order to control the axialuniformity of the winding, and to actively damp the vibrations producedin the growing roll.

[0043] The device for controlling the rotation of the core isadvantageously operatively connected to the device for rotating thepulling drum so as automatically to regulate the uniformity of thecompactness of the roll being wound upon variations of the speed ofsupply of the web material.

[0044] With further advantage, each carriage 49, 49′ is moved along atleast one of the movement axes defined by the guides 51, 54 and 51′, 54′in controlled manner. For this reason, as already mentioned, thecylinder and piston units 56, 56′ and the geared motor units 58, 58′ areoperatively connected to the operating devices 59 and to the controldevices 60 with speed and/or movement feedback, for example, by means ofspeed and/or movement transducers connected to the movement devices 56,56′ and 58, 58′ and/or to the sliding blocks 52, 52′ and to thecarriages 49, 49′, respectively. By virtue of the controlled operation,advantageously with feedback, it is possible to move the core along theworking path “P”, controlling its position relative to the winding drums23, 26 at every moment, and to control the steps of picking up the corefrom the flat springs 35 (pick-up position “L”) and releasing it in therelease position “U”. The controlled movement of the cylinder and pistonunits 56, 56′ also enables an axial pulling force to be applied to thecore 5 gripped by the springs 42 of the pins 37, reducing its bendingdeformation brought about by its own weight and by the weight of the webmaterial wound on it and reducing or eliminating the vibrations producedby the winding operation. The controlled operation of the means formoving the core 5, advantageously with feedback, also enables the core 5to be influenced so as to keep the roll 8 being formed continuouslybearing against the winding drums 23, 26, ensuring that it is guidedsecurely and supported throughout the increasing portion of the workingpath “P”.

[0045] A description of the operation of a rewinding machine accordingto the present invention is given below.

[0046] The web material is drawn into the rewinding machine by thepulling drum, operated in controlled manner and preferably with feedbackof the value of the tension imparted to the web material, defining theproduction rate of the rewinding machine. This rate of operation of themachine is set by the control device, for example, a numerical controldevice arranged for controlling all of the operations. The tension whichis produced in the web material in various portions of its path, as wellas its speed are thus influenced by the predefined speed set for thepulling drum.

[0047] When the rewinding machine is started, predefined timing rulesare imposed on the operation of the pulling drum and, in particular,predefined acceleration rules, for example, depending on the type of webmaterial supplied, so as to enable the nominal speed of the machine tobe reached in as short a time as possible whilst maintaining thesynchronism of operation of all of the parts making up the machine andensuring optimal production quality.

[0048] The web material moved by the pulling drum is supplied to thepre-cutting unit where the web material is pre-cut transversely atregular intervals, in known manner.

[0049] When the pre-cutting has been performed, the web material issupplied to the winding unit where it is guided by the winding drum tothe vicinity of the working path “P” in order to be collected by a corein the manner which will be described below. The winding drum isconnected electronically to the device for operating and controlling thepulling drum so that the pull on the web material is kept constant andthe occurrence of excessive stresses therein which might lead tobreakages at the pre-cut points is prevented. According to oneembodiment, the device for operating and controlling this winding drumconstitutes a reference for the second winding drum and for the meansfor moving the core. In particular, the second winding drum iselectronically connected to the device for operating and controlling thefirst winding drum so as to permit variations in the peripheral velocityof the second winding drum in order to regulate the consistency orcompactness of the roll being wound. This electrical connection alsoinfluences the rate of rotation imposed by the pins on the core and thespeed of movement of the core along the increasing portion of theworking path “P”.

[0050] The cores are supplied to the pick-up position “L” of the workingpath “P” by virtue of the intermittent movement of the supply devicedescribed above.

[0051] The movement of the cores along the working path “P” is achievedby imposing particular timing rules on the device for operating andcontrolling the cylinder and piston units as well as on the geared motorunits acting on the carriages and on the sliding blocks provided in thetables with crossed guides. In particular, a first pair of opposed pins,operated and controlled in reflectively symmetrical and synchronousmanner or, in other words, in electrical alignment, is aligned with acore disposed in the pick-up position “L” and is moved towards the coreso as to insert the pins in its opposed tubular ends until the annularprojection of each pin is brought into abutment with the edge of thecore. The geared motor units, acting by means of the racks on thecarriages, extract the core from the loader with flat springs by amovement along the approach portion of the working path “P”. Once thecore has been picked up, the motors for rotating the pins are operatedso as to bring the peripheral velocity of the core substantially to theperipheral velocity of the winding drum and of the web material guidedthereby, facilitating the initial gripping of an edge of the webmaterial by the core which has been brought to the pick-up position “F”between the two winding drums. When the edge has been gripped by thecore, the web material, guided by the winding drum, is wound onto thecore, which is rotated in controlled manner, to form a roll. During thisstage of the winding of the roll, the core is moved away from thegripping position “F”, that is, the diametral point, or the point atwhich the gap between the winding drums is smallest, travelling alongthe increasing portion of the working path. During the enlargement orincrease of the roll, the rate of rotation of the core is reduced sothat the peripheral velocity of the roll being formed substantiallycorresponds to the peripheral velocity of the winding drum, or differsby a predefined velocity value, in order to control the compactness orconsistency of the roll being formed. The timing rules by which the rateof rotation of the core is reduced are also set in dependence on thecalculated movement of the core in the increasing portion of the workingpath “P” as well as on the thickness of the web material. During thesize enlargement or increasing, the core is advantageously moved awayfrom the pick-up position so that the roll is kept continuously bearingagainst the winding drums. Upon completion of the winding, the roll isseparated from the web material guided by the winding drum, for example,by tearing in the region of a pre-cut line previously made in the webmaterial. This tearing advantageously takes place without the use offurther devices for cutting or stopping the web material. In particular,upon completion of the formation of the roll, an abrupt movement of thecore away from the final winding position “E” and, together therewith orseparately, an abrupt acceleration of the rotation of the core, areimparted to tear the web material. When the tearing has taken place, thepins are extracted from the ends of the core in the release position“U”, by an axial movement of the pins, leaving the roll free to fall bygravity onto the discharge chute. The pins then return to the pick-upposition, still with a synchronized and reflectively symmetricalmovement, to perform a new cycle (FIGS. 4, 5 and 6).

[0052] By virtue of the fact that it is possible to bring aboutout-of-phase rotation of the two opposed pins engaged in the ends of acore, it is possible to control and to regulate the twisting of the coreduring the winding and particularly at the beginning of the winding whenundesired flexural and/or torsional oscillations arise in the roll beingformed.

[0053] During the stage of the enlargement of the roll of web materialwound on the core, the core is subjected to an axial pulling actionwhich is facilitated by the provision of springs having arms withblade-like ends for grasping the end portion of the core. This pullingaction brings about a stiffening of the core and hence an adequatesupport for the web material being wound and also opposes bending due toa long length or axial extent of the core, which would favour theestablishment of vibrations during the winding stage.

[0054] Whilst one pair of opposed pins is performing the winding, thesecond pair of pins prepares for the movement of a subsequent core. Thissecond pair performs the above-described winding cycle before theprevious core inside the roll is released, so that the edge of web.material released by the tearing brought about by the movement of theprevious core is picked up on this subsequent core. Whilst a first pairof pins expels its roll, the other pair of pins performs the winding ofa subsequent roll, permitting a continuous cycle without dead times.

[0055] It can be appreciated from the foregoing that the proposedrewinding machine permits the use of long cores. The fact that the rollbeing formed is arranged to bear constantly on at least one winding drumprevents undesired bending which arises in known central windingmachines.

[0056] An advantage is that it is possible to achieve the desiredconsistency of the roll by virtue of the synergy provided between theforward movements, the controlled rotation, and the support of the rollbeing formed on at least one winding drum. In particular, with theproposed rewinding machine, it is possible to wind the web material ontothe core with a predetermined and uniform consistency throughout thethickness of the roll.

[0057] As well as supporting the core during winding, the provision ofopposed motor-driven pins enables the rotation of the core to beimparted directly in order to achieve accurate control of the windingand to affect directly the compactness of the web material rolled, aswell as preventing both flexural and torsional vibrations produced inthe roll.

[0058] By differentiating the speeds of rotation of the ends of thecore, it is possible to affect the oscillation of the roll being formed.

[0059] Each end of the core can be moved independently of the other,enabling the parallelism of the axis of the roll relative to the axes ofthe drums to be regulated and enabling the formation of the roll to becontrolled, that is, preventing rolling deformities between one end ofthe roll and the other.

[0060] The ability to exert an axial pull on the core enables the coreto be stiffened, further reducing its bending and the winding deformityof the web material.

[0061] The rewinding machine proposed avoids the need to use separateand complex means for cutting with blades or tearing by stopping, andenables the roll wound to be separated from the web material simply byaccelerating the rotation of the core and/or abruptly accelerating theonward movement of the roll, achieving structural simplicity and morereliable operation of the machine.

[0062] The provision of two pairs of opposed pins enables continuity ofproduction of the rolls to be achieved, avoiding abrupt slowing-down andacceleration of the web material.

[0063] By virtue of the preliminary rotation of the core along theapproach portion of the working path, the contact between the core andthe web material is gentle. This prevents undesired breakage of the webmaterial during the first stages of the winding and, above all, preventsthe first coils of material wound on the core from being stretched,avoiding an appearance of poor quality being imparted to the roll.

[0064] Clearly, variants and/or additions may be provided for theembodiment described and illustrated above.

[0065] As an alternative to the embodiment shown in the drawings,instead of using cylinder and piston units as well as racks and pinionsfor moving the pins towards and away from the core and along the workingpath, recirculating ball screws operatively connected to electric motorsor, preferably, linear electric motors may be used.

[0066] As an alternative to the embodiment described above, the pins maybe keyed directly to a shaft of an electric motor or, in other words,direct drive of the pins, or motor-driven pins, may be provided.

[0067] The device for the support, controlled rotation, and movement ofthe cores (the table with crossed guides) may advantageously be formedindependently of the provision of continuous support for the roll beingwound on at least one drum so as to operate in accordance with a centralwinding method.

[0068] As an alternative to the embodiment described above, it ispossible to provide a core constituted by two half-cores which can beconnected to one another and can be removed from the material woundthereon, to form rolls without cores.

[0069] It is advantageously possible to provide a control of themovement of the core along the working path “P” with feedback by asignal proportional to the thickness of the web material in order toconstitute a further control of the consistency of the roll beingformed.

[0070] In order to satisfy contingent and specific requirements, aperson skilled in the art may apply to the above-described preferredembodiment of the rewinding machine many modifications, adaptations andreplacements of elements with other functionally equivalent elementswithout, however, departing from the scope of the appended claims.

What is claimed is:
 1. A rewinding machine for winding web material ontoa core to form rolls, comprising: supply means for supplying the webmaterial at a predefined supply speed, a winding drum rotating with aperipheral velocity substantially corresponding to the supply speed andconstituting a guide for the web material, gripping means for supportingthe core, means for moving the core along a working path which isdisposed between a pick-up position and a release position and extendsthrough a position of initial contact of the core with the web materialguided on the winding drum, as well as a subsequent final windingposition, means for the controlled rotation of the core in order to windthe web material onto the core, forming the roll, means for influencingthe core in a manner such that the winding of the web material onto thecore takes place whilst the roll is kept bearing on the winding drumthroughout a increasing portion of the working path defined between theinitial contact position and the final winding position.
 2. A rewindingmachine according to claim 1, comprising a supply device for arrangingthe core in the pick-up position.
 3. A rewinding machine according toclaim 1 or claim 2, comprising means for releasing the core in theposition for the release of the wound roll.
 4. A rewinding machineaccording to claim 1 in which the winding drum is operated in controlledmanner so as to have a peripheral velocity substantially correspondingto, greater than, or less than the speed of supply of the web material.5. A rewinding machine according to claim 1 in which the winding drum isa first winding drum of a set of winding drums comprising a secondrotating winding drum, spaced from the first winding drum.
 6. Arewinding machine according to claim 5 in which the distance between thesecond winding drum and the first winding drum substantially correspondsto the transverse size of the core.
 7. A rewinding machine according toany one of claims 5 and 6, comprising means for influencing the core ina manner such that the winding of the web material onto the core takesplace whilst the roll is kept bearing both on the first winding drum andon the second winding drum, throughout the increasing portion of theworking path.
 8. A rewinding machine according to claims 5 in which thesecond winding drum is operated in controlled manner so as to have aperipheral velocity substantially corresponding to, greater than, orless than the supply speed of the web material.
 9. A rewinding machineaccording to claim 1 in which the core is a tubular core.
 10. Arewinding machine according to claim 9 in which the means for grippingthe core comprise opposed pins which can be operatively associated withthe insides of the ends of the tubular core.
 11. A rewinding machineaccording to claim 10 in which each of the pins comprises afrustoconical insertion end.
 12. A rewinding machine according to claim10 or claim 11 in which each of the pins comprises retaining means inengagement with the internal surface of the wall of the tubular core.13. A rewinding machine according to claim 12 in which the retainingmeans comprise at least one resilient expansion device housed in atleast one longitudinal channel provided in the pin, the devicepreferably comprising at least one blade-like element acting to opposeslipping-out of the pin.
 14. A rewinding machine according to claim 1 inwhich the gripping means are operatively associated with the means forrotating the core.
 15. A rewinding machine according to claim 1 in whicheach of the means for rotating the core is controlled so as to achieve aperipheral velocity of the roll being wound substantially correspondingto, less than, or greater than the speed of supply of the web material.16. A rewinding machine according to claim 15 in which the means forrotating the core comprise an electric motor operated in controlledmanner.
 17. A rewinding machine according to claim 16 in which theelectric motor is operatively connected to a control device.
 18. Arewinding machine according to claim 17 in which the control device isoperatively connected to a device for the control of the supply means.19. A rewinding machine according to claims 15 in which a device isinterposed between the gripping means and the controlled rotation meansfor detecting the force transmitted between them, the device beingoperatively connected to a device for the controlled operation of themeans for rotating the core.
 20. A rewinding machine according to claim1 in which independent means are provided for the controlled rotation ofeach end of the core.
 21. A rewinding machine according to claim 20 inwhich the independent means for rotating the core are operativelyconnected to a control device for their synchronized or out-of-phaseoperation.
 22. A rewinding machine according to claim 1 comprising meansfor pulling the core axially during the winding of the web material. 23.A rewinding machine according to claim 22 in which the means for pullingthe core axially comprise opposed carriages facing the ends of the coreand slidable on guides arranged transverse the working path.
 24. Arewinding machine according to claim 23 in which each of the opposedcarriages is operatively connected to a controlled actuation device. 25.A rewinding machine according to claim 24 in which the actuation deviceof each carriage comprises a hydraulic or pneumatic cylinder and pistonunit or a linear electric motor, operated in controlled manner.
 26. Arewinding machine according to claim 24 in which the actuation device ofeach carriage comprises a rack and pinion unit operatively connected toa motor, operated in controlled manner.
 27. A rewinding machineaccording to claim 24 in which the actuation device of each carriagecomprises a recirculating ball screw unit operatively connected to amotor, operated in controlled manner.
 28. A rewinding machine accordingto claim 1 in which the means for gripping the core are operativelyconnected to the means for moving the core.
 29. A rewinding machineaccording to claim 28 in which the moving means comprise carriagesarranged facing one another in the vicinity of the ends of the core, thecarriages being movable along movement axes arranged parallel to andperpendicular to the working path, in the manner of a table with crossedguides.
 30. A rewinding machine according to claim 29 in which each ofthe carriages is moved along the axes by at least one actuating device.31. A rewinding machine according to claim 30 in which the at least oneactuating device of each carriage comprises at least one hydraulic orpneumatic cylinder and piston unit.
 32. A rewinding machine according toclaim 30 in which the at least one actuating device of each carriagecomprises at least one rack and pinion unit operatively connected to amotor.
 33. A rewinding machine according to claim 30 in which the atleast one actuating device of each carriage comprises at least onerecirculating ball screw unit operatively connected to a motor.
 34. Arewinding machine according to claim 30 in which each carriage is movedalong at least one of the movement axes in controlled manner.
 35. Arewinding machine according to claim 1 in which independent means areprovided for moving each end of the core.
 36. A rewinding machineaccording to claim 35 in which each of the independent means for movingthe core is operatively connected to a control device for theirsynchronized or out-of-phase operation.
 37. A rewinding machineaccording claim 1 in which twin independent gripping means are providedand can be associated with ends of cores on the same side or side wallof the rewinding machine.
 38. A rewinding machine according to claim 1in which twin independent means are provided for the controlled rotationof the core and can be associated with ends of cores on the same side orside wall of the rewinding machine.
 39. A rewinding machine according toclaim 1 in which twin independent means are provided for moving the coreand can be associated with ends of cores on the same side or side wallof the rewinding machine.
 40. A rewinding machine according to claim 1in which twin independent means for influencing cores bearing on thewinding drum are provided for each side of the rewinding machine.
 41. Arewinding machine according to claim 1 in which the supply meanscomprise a drum for pulling the web material, operatively connected to amotor operated in controlled manner.
 42. A rewinding machine accordingto claim 41 in which the motor is operatively connected to a controldevice for the operation of the pulling drum in synchronism or out ofphase with the winding drum as well as with the gripping means, and themeans for moving, rotating and influencing the core bearing on thewinding drum.
 43. A rewinding machine according to claim 41 or claim 42in which a device is provided, between the pulling drum and the motor,for detecting the force transmitted between them, the device beingoperatively connected to a device for controlling the motor.
 44. Arewinding machine according to claim 1 in which means are provided fordetecting the thickness of the web material.
 45. A rewinding machineaccording to claim 1 in which the means for detecting the thickness ofthe web material are operatively connected to the device for controllingthe movement of the core for the winding of the web material thereon.46. A rewinding machine according to claim 1 in which the supply devicecomprises a chute for transporting the core towards restraining meansdisposed in the vicinity of the winding drum, defining the pick-upposition.
 47. A rewinding machine according claim 1 in which the meansfor influencing the core bearing against the winding drum comprise atleast one resilient device.
 48. A rewinding machine according to claim47 in which the means for influencing the core bearing on the windingdrum comprise a spring or a pneumatic device.
 49. A rewinding machine(1) for winding web material (7) on a core (5) in order to form rolls(8) in which the web material is supplied to a winding drum (23) and theweb material is transferred to the core to form the roll, characterizedin that the core is supported, rotated in controlled manner, andtransported along a path in which the roll of web material wound on thecore (P) is increased whilst bearing continuously on the winding drum.50. A method of winding web material on a core to form rolls, in which:the web material is supplied at a predefined supply speed, and the webmaterial is guided, in a winding region, at a speed substantiallycorresponding to the supply speed, the core is supported and is rotatedin a manner such as to have a predefined peripheral velocity, the coreis moved along a working path formed between a pick-up position and arelease position, passing from a position of initial contact of the corewith the web material in order to pick up the web material andcontinuing towards a final winding position, through a increasingportion in which the material is wound on the core forming the roll, andthe core is influenced in a manner such that the material is wound ontothe core whilst the roll being formed is kept bearing on the windingdrum throughout the increasing portion of the working path.
 51. A methodof winding web material according to claim 50 in which the core isreleased, when the roll is fully wound, in the release position of theworking path.
 52. A method of winding web material according to claim 51in which, before the core is released, the rotation of the core isaccelerated and/or, together therewith or separately, the core is movedabruptly away from the winding drum to separate the web material alreadywound on the core from the material being supplied.
 53. A method ofwinding web material according to claim 52 in which the separation takesplace by tearing.
 54. A method of winding web material according toclaims 50 in which the roll being formed is influenced, whilst bearingon a further, second winding drum.
 55. A method of winding web materialaccording to claims 50 in which the forward movement of the core alongthe increasing portion of the working path is controlled in order toinfluence the roll being formed, bearing on the winding drum.
 56. Amethod of winding web material according to claims 50 in which the coreis disposed in a pick-up position from which it is picked up and movedalong the working path.
 57. A method of winding web material accordingto claim 56 in which the core is picked up from the pick-up position bybeing supported at its ends.
 58. A method of winding web materialaccording to claim 50 in which the ends of the core are rotatedindependently of one another and in a synchronized or out-of-phasemanner.
 59. A method of winding web material according to claim 50 inwhich torsional vibrations of the core are compensated by rotation ofits ends in a controlled and independent manner by differentiation oftheir rates of rotation.
 60. A method of winding web material accordingto claim 50 in which the core is subjected to an axial pulling forceduring the stage of the winding of the web material.
 61. A method ofwinding web material according to claim 50 in which the ends of the coreare moved along the working path independently of one another and in asynchronized or out-of-phase manner.
 62. A method of winding webmaterial according to claim 50 in which non-uniformity of winding of theweb material on the core is compensated by moving its ends along theworking path independently.
 63. A method of winding web materialaccording to claim 50 in which the core is rotated before it comes intocontact with the web material so that its peripheral velocity issubstantially equal to the speed of movement of the web material to bepicked up in order to be wound around the core.
 64. A method of windingweb material according to claim 50 in which the rate of rotation isreduced during the winding of the web material onto the core so as tomaintain a predefined peripheral velocity of the roll being formed,throughout the winding stage.
 65. A method of winding web materialaccording to claim 50 in which the force transmitted to the web materialin order to supply it at a predefined speed is detected.
 66. A method ofwinding web material according to claim 50 in which the thickness of theweb material is detected.
 67. A method of winding web material accordingto claim 66 in which the movement and/or the rotation of the core alongthe increasing path is controlled on the basis of operative parametersincluding the thickness detected.